Work has been carried out on a number of structural problems related to proteins derived from the HIV-1 virus. Three dimensional solution structures of Nef , the N-terminal domain of HIV-1 integrase and the complete ectodomain of SIV gp41 have been determined. In addition the structure of a host factor, HMG-I/Y, complexed to DNA, and that of the barrier to autointegration factor, BAF, which are essential for the formation of the preintegration complex, have been solved. Finally, the structure of cyanovirin-N, a 11 kDa highly potent inhibitor of HIV has been solved.